Printing device

ABSTRACT

The present invention provides a printing device capable of high-resolution reproduction of documentary images and ensuring satisfactory productivity. Specifically, the invention provides a printing device which ejects only ink or a printing device which mixes/ejects ink and diluent, both of which has at least the periphery of the nozzle member on the side upon which the nozzle opens its mouth made of polybenzimidazole or polyimide.

This application is a divisional of patent application Ser. No.08/831,827, filed Apr. 2, 1997; now U.S. Pat. No. 6,074,039.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to printing devices. The presentinvention specifically relates to a printing device that ejects anejecting medium, and to a printing device that mixes and ejects meteringand ejecting media. More specifically, this invention relates to aprinting device that has the surface of a nozzle member made ofpolybenzimidazole, which allows high-resolution reproduction ofdocumentary images and improved productivity. Moreover, the inventionhaving the nozzle member made of polybenzimidazole is capable of beingmanufactured by pressure molding or injection molding, which alsopromotes improved productivity.

2. Description of the Related Art

Recently, preparation of documents based on computer systems, such asso-called desk top publishing, is favored by clerks in offices. Alongwith such tendency, a growing need exists among such people for amachine capable of faithfully reproducing images of natural objects inphotos together with characters and figures. As a result, a strongdemand exists for a high-grade printing device capable of high-qualityprinting of the images of natural objects. For such printing device tobe produced, it is important to reproduce intermediate tones faithfully.

A printer which, only when it receives printing signals, ejects inkdroplets through a nozzle onto a printing medium, such as paper andfilm, or a so-called on-demand type printer have spread quickly inrecent years because they can be small in size and produced at a lowcost.

A variety of methods have previously been proposed for ejecting inkdroplets. However, the methods dependent on the use of a piezoelectricelement or a heating element have been generally used. The formerconsists of ejecting ink under the pressure wrought by a deformedpiezoelectric element, and the latter depends on the pressure of bubbleswhich develops when ink is heated to a boiling point with a heatingelement.

A variety of methods have also been previously proposed to provide anon-demand type printer, as described above, capable of reproducingintermediate tones faithfully. One such method is to control the size ofdroplets by adjusting the voltage or width of an electric pulse appliedto a piezoelectric element or a heating element, so that the size ofprinted dots corresponds well with the intermediate tone to bereproduced. With this method, however, if the voltage or width of thepulse delivered to the piezoelectric element or the heating element ischosen too small, ink will not be ejected. Thus, the size of thesmallest droplet has a certain limit. This imposes a number oflimitations to this method: reproducible tone gradations is limited innumber; reproduction of low tones is particularly difficult; andsatisfactory reproduction of the images of natural objects can scarcelybe achieved.

A second method does not depend on the alteration of dot size. Instead,this method uses pixels each comprising a matrix of 4×4 dots andreproduces tones by adjusting the density of pixel depending on thenumber of excited matrices, or by using the so-called dither method. Inthis case, each pixel can reproduce 17 different tones. However, when atest pattern with a certain dot density is printed by the two methods,and both printings are compared, the printing by the second method has aresolution one fourth that by the first method. Accordingly, theprinting achieved by the second method is too rough to be applied forreproducing the images of natural objects.

In view of this, the present inventors have proposed a printing devicecapable of faithfully reproducing the images of natural objects withoutimpairing resolution. In this regard, concentration of an ejecting inkdroplet can be varied by the addition of diluent to the ink duringejection, so that the printed density of ink can be controlled.

A printing head suitable for such printing device should have a firstnozzle member for ejecting medium and a second nozzle member formetering medium placed close to each other. A predetermined volume ofthe metering medium is pressed out from the second nozzle member towardsthe first nozzle member to be mixed with the ejecting medium in closevicinity to the orifice of the first nozzle member, so that the ejectingmedium can be ejected out together with the metering medium and therebyto effect mixing/ejection of the metering and ejecting media. In theprinting device with such printer head, the volume of a metering mediumcontaining either ink or diluent can be varied so that the mixing ratioof ink and diluent can be varied, which enables alteration of dotdensity. This enables faithful reproduction of the images of naturalobjects. The metering medium and the ejecting medium can be either inkor diluent; when one is ink, the other is diluent, and vice versa.

A printing device that exercises mixing/ejecting ink and diluent toachieve a faithful reproduction of an image controls the mixing ratio ofink and diluent precisely according to the tone of the image to beprinted. For this to be achieved, ink and diluent must be kept separatedwhen they are not mixed or when they are at a stand-by state. If theyare in contact with each other while they are at a stand-by state, inkand diluent will diffuse mutually into the other's nozzle: ink to adiluent nozzle and diluent to an ink nozzle. This inadvertent mixture ofink and diluent will gravely affect the mixing ratio of ink and diluentin dots subsequently printed, thereby making it impossible to faithfullyreproduce the tone of an image. Accordingly, such printer head will notallow high-resolution reproduction of documentary images. In view ofthis, providing a space between the orifices of the metering mediumnozzle and of the ejecting medium nozzle with a liquid-repellentproperty is desirable.

This invention is also applicable to a printing device furnished onlywith an ink nozzle, because adherence of ink around the orifice of theink nozzle would interfere with smooth ejection of subsequent ink fromthe orifice so that ink ejection would become instable in its direction.Accordingly, such printer head will not allow high-resolutionreproduction of documentary images either.

Adherence of ink around the orifice of the ink nozzle would readilyoccur in the printing device furnished with the ink and diluent nozzles,unless a liquid-repellent property is conferred to a space between thetwo nozzles. The liquid-repellent substance previously used for thepresent purpose generally includes polytetrafluoroethylene or the like.Such substance is applied around the orifices of the nozzles of suchprinting devices as described above.

As the form of nozzles, particularly of their orifices, gravely affectsthe direction of liquids ejected from the nozzles, and thus the qualityof printed characters, it is conventional to process the nozzles byabrasion with an excimer laser. Abrasion with excimer laser, however,cannot be applied to polytetrafluoroethylene or similar type compounds.To address such inconvenience, a method such as that disclosed inJapanese Unexamined Patent Publication No. 6-328698 is proposed where amaterial capable of absorbing light whose wave length corresponds tothat of an excimer laser is allowed to disperse inpolytetrafluoroethylene, and the resulting compound is processed withthe excimer laser to prepare a nozzle.

With the method as described in Japanese Unexamined Patent PublicationNo. 6-328698, however, amenability of a material to processing byabrasion with excimer laser and the liquid-repellency of the processedmaterial can scarcely be compatible: when the former is emphasized, thelatter is more or less sacrificed, and vice versa. Further, abrasionwith excimer laser, when applied to prepare a nozzle in the considerablythick substance of a film made of polytetrafluoroethylene, can scarcelyallow fine processing, which will easily result in development of minuteflaws around the processed parts.

Moreover, abrasion with excimer laser is rather complicated inoperation: management of gas and the optical system is cumbersome, andlarge amounts of materials must be consumed in association. These thingswill contribute to raise the cost for production. In view of this, it isdesirable when abrasion with excimer laser is applied for the formationof a nozzle of the printer head of the above-described printing device,to reduce the time necessary for abrasion as much as possible. This willbe accomplished by combining injection molding and abrasion with excimerlaser, as is disclosed in the above-described Japanese Unexamined PatentPublication No. 6-328698. Specifically, a resin such as polysulfone orthe like is subjected to injection molding to produce a film that has araw form of nozzle formed therein to which a liquid-repellent membraneas described above is applied. Then, abrasion with excimer laser isapplied to this assembly, to bore a hole through the polysulfone filmand the liquid-repellent membrane. This procedure allows fine workingnecessary for preparation of the nozzle orifice and its vicinity whoseconfiguration gravely affects the direction the droplet takes whenejected.

When polysulfone or a material having a thermal resistance up to 180° C.is used for this purpose, the material to be used for the formation ofthe liquid-repellent membrane should polymerize at around 150° C.Further, as described above, the material is necessarily limited topolytetrafluoroethylene having a material dispersed therein that canabsorb the light having the same wave length with an excimer laser usedfor abrasion. These impose severe restrictions on the choice ofappropriate materials. This will result in lowered productivity.

Further, if polysulfone is used as a material for the purpose hereconcerned, because its thermal resistance is rather low, variousrestrictions will be imposed. For example, a restriction will be imposedon the processes subsequent to the formation of the nozzle, such asbonding of other members onto the nozzle surface. This will likewiseresult in lowered productivity.

Therefore, a need exists for an improved printer head and methods forpreparing same that enable the faithful reproduction of documentaryimages while also promoting productivity.

SUMMARY OF THE INVENTION

The present invention provides printing devices that address theproblems inherent in conventional printing devices. The presentinvention provides a printing device that ensures liquid-repellency ofthe periphery of nozzle orifices, thereby enabling faithful reproductionof documentary images, enabling formation of nozzles by abrasion withexcimer laser, and allowing a satisfactory productivity. Additionally,the present invention provides a printing device capable of having itsnozzle members made of a wide variety of materials, and prepared byvarious procedures or their combinations, including injection molding.As a result, the invention of the present application promotessatisfactory productivity.

The present invention specifically relates to the use ofpolybenzimidazole or polyimide compounds as materials of the printerhead of the printing device. Use of such materials ensure theliquid-repellency of the nozzle member, and allows those parts to beprocessed by abrasion with excimer laser. More specifically, in anembodiment, the printing device of the present invention has in itsprinter head, which has a chamber to contain an ejecting medium and anozzle member to communicate with that chamber, at least the peripheryof the nozzle orifice and/or the nozzle body made of a polybenzimidazoleor a polyimide compound. Thus, the nozzles of the present invention canbe made of a wide variety of materials and can be formed by variousprocedures and their combinations, including injection molding.

In another embodiment, the printing device of the present invention hasa printer head having a first chamber containing an ejecting medium anda second chamber containing a metering medium. In the printing head, afirst nozzle member communicates with the first chamber and a secondnozzle member communicates with the second chamber, such chambers beingplaced adjacent to each other. For purposes herein, such nozzle membershave a nozzle orifice (outer portion) and a nozzle body (inner portion).At least the periphery of the nozzle orifice and the nozzle body aremade of polybenzimidazole or polyimide.

Pursuant to the present invention, the polybenzimidazole to be used as amaterial for the periphery of the nozzle orifice may include variouschemicals. Preferably, the polybenzimidazole includes chemicals havingthe structure of the following Formula A:

wherein n represents a positive integer.

The polybenzimidazole preferably has a water-absorbing property of 4.0%or less, when left in an atmosphere of 76% RH for 24 hours. For example,PBI matrix resin solution can be used as such polybenzimidazolecompound. A commercially available solution that may be used is acerazol painting grade solution available from Hoechst and is sold underthe trademark NPBI.

In an embodiment, other portions of the printer head, including thenozzle body and chambers containing the fluids, may also be made ofpolybenzimidazole. The polybenzimidazole to be used as a material forsuch other portions of the printer head may include various chemicals.Preferably, the other portions of the printer head, aside from theperiphery of the nozzle orifice, include chemicals having the structureof the following Formula B:

where n represents a positive integer.

When the periphery of the nozzle body, as well as other portions of theprinter head, is made of polybenzimidazole as indicated above, it canpreferably be processed by pressure molding or by injection molding. Anexample of a suitable polybenzimidazole that can be used is availablefrom Hoechst and is sold under the trademarks U-60 and TU-60. Moreover,when the periphery of the nozzle body is made of such apolybenzimidazole, the periphery of the nozzle orifice may be made of amaterial capable of polymerizing at a temperature of 150° C. or higher.For example, as detailed below, polyimide polymers into which a fluorinepolymer has been dispersed may be used as material for the periphery ofthe nozzle orifice. In an embodiment, such fluorine polymer may be acopolymer of tetrafluoroethylene and hexafluoropropylene.

In another embodiment of the printing device of this invention, at leastboth the periphery of the nozzle orifice and the nozzle body may be madeof polybenzimidazole. The materials as described above may be used suchas polybenzimidazole. In such an embodiment, the polybenzimidazole usedfor the periphery of the nozzle orifice can be a material thatpolymerizes at a considerably higher temperature of more than 300° C.

Since the periphery of the nozzle orifice is made of polybenzimidazole,the present invention ensures liquid-repellency around the periphery ofthe nozzle orifice. In addition, the printing device of this inventionallows the nozzle to be formed with a laser. Preferably, the nozzle isformed by abrasion with an excimer laser.

Moreover, as detailed above for the printing device of this invention,other portions of the printer head, namely the parts excluding theperiphery of the nozzle orifice (i.e. nozzle body), may be made ofpolybenzimidazole or polyimide. Because these substances are highlyresistant to heating, the periphery of the nozzle orifice can be made ofa material that polymerizes at a considerably higher temperature than150° C. Because such materials are necessarily suitable for abrasionwith excimer laser, the printing device of this invention will thusallow the nozzle orifice of the printing head to be processed byabrasion with excimer laser. When other portions of the printer head aremade of polybenzimidazole, the nozzle can be formed by a methodincluding abrasion with excimer laser or the like.

Further, as mentioned above, at least the periphery of the nozzleorifice can be made of a polyimide polymer in which a fluorine polymeris dispersed. The fluorine polymer may include various chemicals.Preferably, the fluorine polymer includes a copolymer oftetrafluoroethylene and hexafluoroethylene or the like which have astructure as represented by the following Formula C:

where m and n are mole percentages; m being a positive integer from 1 to99 and n being a positive integer from 99 to 1. An example of a suitablefluorine polymer that may be used is available from DuPont and is soldas Teflon® coating 958-207. The polyimide polymer may have a property topolymerize when heated to 300° C. of higher.

In another embodiment, the polyimide polymer, besides those mentionedabove, may include various chemicals including aromatic polyimides. Itmay include further the compounds which have a structure as representedby the following Formula D and Formula E:

where n represents a positive integer; and R is any divalent bridgingunit. For example, R can be one of the following units: O, CO, CH₂, orC₂H₄.

where n represents a positive integer. Such polyimide polymerspreferably have a water absorbance of 0.4% or less when kept in water of23° C. for 24 hours. Such polyimide polymers may further have a propertyto polymerize when heated to 180° C. or lower.

In an embodiment, the polyimide polymer may include polyimidesiloxane.The polyimidesiloxane preferably has a structure as represented by thefollowing Formula F and Formula G:

where k, l, m and n represent positive integers; R is a divalentbridging unit; R₁ can be CH₂, (CH₂)₂, (CH₂)₃, (CH₂)₄, or (CH₂)₅; and R₂can be CH₃, C₂H₅, or C₃H₇.

where k, l, m and n represent positive integers; R is a divalentbridging unit; R₁ can be CH₂, (CH₂)₂, (CH₂)₃, (CH₂)₄, or (CH₂)₅; and R₂can be CH₃, C₂H₅, or C₃H₇.

The polyimidesiloxane is preferably a compound which results afterhaving part of its aromatic hydrocarbon component substituted bysiloxane, and has a 3-25 weight % of Si with respect to polyimide.Suitable polyimide polymers, for example, that satisfy theserequirements are available from Ube Industries and are sold under thetrademarks Yupicoat FS-100L and Yupifine FP-100.

In yet another embodiment, the polyimide polymer, besides those detailedabove, may include compounds having a structure as represented by thefollowing Formula H:

where m represents a positive integer. Such a suitable polyimide polymeris a coating type polyimide sold under the trademark PIQ6400 provided byHitachi Chemicals.

In an embodiment therefore, the printing device of this invention has atleast the periphery of the nozzle orifice made of a polyimide polymer inwhich a fluorine polymer is dispersed, thereby ensuringliquid-repellency around the periphery of nozzle orifice. In addition,because the polyimide polymer can be appropriately processed by abrasionwith excimer laser, the printing device of this invention allows thenozzle to be formed by abrasion with an excimer laser.

In another embodiment, parts other than the periphery of the nozzleorifice (i.e. nozzle body and medium chambers), are made of a secondpolyimide polymer with a dispersion of a fluorine polymer. Because thesesubstances are highly resistant to heating, the periphery of the nozzleopening can be made of a material that polymerizes at a considerablyhigh temperature of about 300° C.

The fluorine polymer and polyimide polymer used for the liquid-repellentmembrane may include the compounds as described above. For example,Teflon® coating 958-207 available from DuPont or a copolymer oftetrafluoroethylene and hexafluoropropylene can be used as the polyimidepolymer with a fluorine polymer dispersed within.

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the detailed description of thepresently preferred embodiments as well as the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the cross-section of a first printingdevice according to this invention.

FIG. 2 is an enlarged view of part of the first printing deviceaccording to this invention.

FIG. 3 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating the procedures of afirst method used to produce the printer.

FIG. 4 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to prepare aliquid-repellent membrane according to the first method of the presentinvention.

FIG. 5 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to prepare anozzle according to the first method of the present invention.

FIG. 6 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to arrange avibrating plate, etc., into a printer head according to the first methodof the present invention.

FIG. 7 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating the procedures of asecond method used to produce the printer, particularly a procedure toprepare a metal plate with a polymer film bonded thereupon.

FIG. 8 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to prepare aliquid-repellent membrane according to the second method of the presentinvention.

FIG. 9 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to prepare anozzle according to the second method of the present invention.

FIG. 10 is a schematic diagram of the cross-section of a second printingdevice according to this invention.

FIG. 11 is an enlarged view of a part of the second printing deviceaccording to this invention.

FIG. 12 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating the procedures of athird method used to produce the printer, particularly a procedure toprepare a base plate.

FIG. 13 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to prepare aliquid-repellent membrane according to the third method of the presentinvention.

FIG. 14 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to preparenozzles according to the third method of the present invention.

FIG. 15 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to arrange avibrating plate, etc., into a printer head according to the third methodof the present invention.

FIG. 16 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating the procedures of afourth method used to produce the printer, particularly a procedure toprepare a metal plate with a polymer film bonded thereupon.

FIG. 17 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to prepare aliquid-repellent membrane according to the fourth method.

FIG. 18 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to preparenozzles according to the fourth method of the present invention.

FIG. 19 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating the procedures of afifth method used to produce the printer, particularly a procedure toprepare a base material.

FIG. 20 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating the procedures of afifth method used to produce the printer, particularly a procedure toprepare a base plate.

FIG. 21 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to prepare aliquid-repellent membrane according to the fifth method of the presentinvention of the present invention.

FIG. 22 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to prepare anozzle according to the fifth method of the present invention.

FIG. 23 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating the procedures of asixth method used to produce the printer, particularly a procedure toprepare a base material.

FIG. 24 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating the procedures of asixth method used to produce the printer, particularly a procedure toprepare a base plate.

FIG. 25 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to prepare aliquid-repellent membrane according to the sixth method of the presentinvention.

FIG. 26 is a schematic diagram of the cross-section of the printingdevice according to this invention illustrating a procedure to preparenozzles according to the sixth method of the present invention.

DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The present invention, in an embodiment, provides an improved printingdevice constructed as to eject only ink as an ejecting medium. Theprinting device has a printing head as illustrated in FIG. 1. Theprinting head includes an orifice plate member 5 including a nozzlemember 1, an ink-chamber 2, an ink feed channel 3, and an ink feedaperture 4. The nozzle member 1, as identified herein, consists of anozzle orifice 1 a and a nozzle body 1 b. The printer head also includesa piezoelectric element 6 placed opposite to the ink-chamber 2. Inaddition, the printing device is provided with a driving unit and acontrol unit (not shown).

The orifice plate member 5 is composed of a base plate 10 having a firstconcave surface 7, which forms part of the ink-chamber 2, a secondconcave surface 8 shallower in its height than the first concave surface7 and which forms part of the ink feed channel 3, a third concavesurface 9 deeper in its height than the second concave surface 8 andwhich forms part of the ink feed aperture 4. The surfaces are preparedin such a way that their open sides intercommunicate with each other andare flush with a main surface 10 a. And, the surfaces have a passageformed from the first concave surface up to a surface 10 b, or a surfaceopposite to the surface 10 a to make a nozzle therefrom. A vibratingplate 11 is attached onto the 10 a side of the base plate to allow it toact as a lid covering for the concave surfaces. Such concave surfacescan take, for example, a form whose cross-section is shaped like a U.Whereas, the nozzle member 1 may take a conical form whose circular,ellipsoid, or rectangular base tapers to a tiny orifice at the backsurface 10 b to form a passage there.

A space between the third concave surface 9 and vibrating plate 11 formsthe ink feed aperture 4. A second space between the second concavesurface 8 and vibrating plate 11 forms the ink feed channel 3. The thirdspace between the first concave surface 7 and vibrating plate 11 formsthe ink chamber 2. Each of these spaces are in fluid communication witheach other and form, together with the nozzle member 1 a continuouspassage for fluid.

Part of the vibrating plate 11 that comes in contact with the thirdconcave surface 9 has an opening 12. To that opening 12 prepared closeto the ink feed aperture 4 is connected an ink feed pipe 13 thatsupplies ink from an ink tank placed outside (not illustrated) to theprinter head. Ink from the ink tank is supplied through the ink feedpipe 13 to the ink feed aperture 4. The ink then passes through the inkfeed channel 3 to the ink chamber 2 and to the nozzle member 1. Thevibrating plate 11 has thin grooves placed on its part so as to make itsportion corresponding to the ink chamber 2 ready to be displaced.

Laminated piezoelectric elements can be used as material composing thepiezoelectric element 6. This embodiment describing the printing deviceconstructed to eject only ink as an ejecting medium incorporates suchlaminated piezoelectric elements. The piezoelectric element 6, asdescribed above, is placed on the part of the vibrating plate 11 whichcorresponds to the ink chamber 2 in such a manner that the long axis ofthe piezoelectric element 6 contacts the vibrating plate at a rightangle. The opposite end is fixed onto a supporting body 15.

The laminated piezoelectric elements composing the pressuring element 6extend/contract in the direction of their long axis. As being stabilizedat one end by a supporting body 15, the piezoelectric element 6, when itextends, exerts a pressure onto the vibrating plate 11 in the directionindicated with arrow P in FIG. 1. In association, ink 14 in the inkchamber 2 is pressurized, and ejected from the nozzle member 1. Duringthis operation, no measurable counter-flow of ink towards ink feedaperture 4 will take place. This is because the ink feed channel 3 isnarrower than the ink chamber 2.

For the printing device of this embodiment to be used for printing, onlythe piezoelectric element 6 is allowed to exert a pressure upon ink 14contained in the ink chamber 2. Then, ink 14 is ejected onto a printingmedium (not illustrated). The tone of an ink dot can be adjusted bychoosing an appropriate size of ink droplet, or number of excited unitdots in the pixel matrix.

The printing head of the printing device of this embodiment, as furtherindicated in the enlarged cross-section in FIG. 2, has aliquid-repellent membrane 16. Membrane 16 is formed at least on theperiphery of the nozzle orifice 1 a of the nozzle member 1 a on the backsurface 10 b or the side of the base plate 10 where the nozzle member 1is formed. As illustrated in FIG. 1, a liquid-repellent membrane isformed all over the back surface 10 b.

This liquid-repellent membrane 16 can preferably be made ofpolybenzimidazole. A variety of chemicals can be used for thepolybenzimidazole. Preferably, chemicals as represented by the followingFormula A are used:

wherein n represents a positive integer. Preferably, thispolybenzimidazole compound has a molecular weight of about 5,000 to1,000,000.

In the printing device of this example, the base plate 10 (encompassingthe nozzle body 1 b) should preferably be made of polyimide or adifferent kind of polybenzimidazole from the above-described one ofFormula A. A variety of chemicals are appropriate for thepolybenzimidazole to be used as a material of the base plate.Preferably, chemicals as represented by the following Formula B are usedfor the polybenzimidazole of the base plate:

where n represents a positive integer. This polybenzimidazole preferablyhas a molecular weight of about 5,000 to 1,000,000. When the base plate10 is made of such polybenzimidazole, it can be preferably processed bypressure molding or by injection molding.

When the base plate 10 is made of polybenzimidazole as described above,the liquid-repellent membrane 16 may be formed of a substancepolymerizing at 150° C. or higher, as well as of polybenzimidazole. Forexample, polyimide polymers into which a fluorine polymer has beendispersed may be used as the liquid-repellent membrane 16. In anembodiment, the fluorine polymer is a copolymer of tetrafluoroethyleneand hexafluoropropylene.

The printing device of this example has a liquid-repellent membrane 16with a liquid-repellency formed at least on the periphery of the nozzleorifice 1 a of the printing head surface upon which the orifice isformed. This arrangement ensures liquid-repellency at the periphery ofthe nozzle orifice 1 a, prevents adhesion of excess ink on the sameplace and contributes to stability of ink ejection, thereby achievinghigh-resolution image formation.

The present invention also provides a method for producing such printingdevice as described above. The description now detailed will focus on amethod for producing such a printer head. As illustrated in FIG. 3, abase plate 10 is so processed as to give a first concave surface 7, asecond concave surface 8 and a third concave surface 9 which opentowards a main surface 10 a. A first concave section 7, second concavesection 8 and third concave section 9 are so processed as to give acontinuous passage, and its configuration is as described above. Asindicated above, the material that may be utilized for this base plate10 includes a polybenzimidazole or polyimide compound. Such material,however, should be a different polybenzimidazole or polyimide from theone used for the liquid-repellent membrane 16.

In a preferred embodiment, polybenzimidazole or polyimide is used forthe base plate 10. The polybenzimidazole used for the base plate 10should preferably have a structure as represented by the above FormulaB. Suitable polybenzimidazole chemicals that may be used, for example,are U-60™ appropriate for pressure molding and TU-6™ appropriate forinjection molding, both available from Hoechst. Such polybenzimidazolecompounds have good wettability, are suitable for processing by abrasionwith excimer laser, allow easy processing of nozzles, and preventpractically all entry of air bubbles into the nozzles. When using apolyimide, any polyimide may be used for the base plate 10 as long as ithas such a grade as to be applied for injection molding. An example of asuitable chemical is polyimide available from Mitsui Toatsu Chemicals.

Then, as illustrated in FIG. 4, a liquid-repellent membrane 16 is formedon a back surface 10 b or the surface opposite to the main surface 10 aof the base plate 10. The liquid-repellent membrane 16 should preferablybe made of such polybenzimidazole and has a structure as represented bythe above Formula A. Such polybenzimidazole should also preferably havea water-absorbing property of 4.0% or less, when left in an atmosphereof 76% RH for 24 hours.

An example of a suitable polybenzimidazole is a PBI matrix resinsolution, such as NPBI™ of cerazol painting grade available fromHoechst. This PBI matrix resin solution is a mixture that results afterpolybenzimidazole has been dispersed in an N,N-dimethylacetoamidesolvent to give a 10 wt % resin solution, and is a liquid mass whoseviscosity is 300±50CP.

The method to apply this mixture onto the base plate 10 may includecoating by spraying, coating by dipping, and electrostatic coatingfollowed by baking at 300° C. or higher for 30 minutes or longer. Aliquid-repellent membrane 16, formed by this method, shows noadhesiveness in a wide temperature range from room temperature to 200°C. Alternatively, a polybenzimidazole material, which satisfies theabove requirements, is allowed to disperse in an N,N-dimethylacetoamidesolvent to give a 10 wt % resin solution. The resulting mixture may thenbe used as a coat on the base plate 10.

When a different polybenzimidazole or polyimide material from the oneused for the liquid-repellent membrane 16 is used as a material for thebase plate 10 as in this embodiment, a baking process requiring heatingexceeding 300° C. or higher can be applied to the base plate 10, whichwould be impossible if the base plate 10 were made of polysulfone orpolyethersulfone.

Then, as illustrated in FIG. 5, a nozzle member 1 is formed with a laserprocessing machine which bores a hole penetrating from the bottom of thefirst concave surface 7 through the base plate 10 and theliquid-repellent membrane 16. With the printing device of this example,a polybenzimidazole or polyimide material making the base plate 10 and asecond polybenzimidazole material making the liquid-repellent membrane16 both allow processing by abrasion with excimer laser, and thus, thenozzle member 1 can be formed through processing by abrasion withexcimer laser. Accordingly, the printing device of this invention allowssimplified processing of nozzles, which contributes to improvement ofproductivity. Moreover, polybenzimidazole and polyimide can be soprecisely processed by abrasion with excimer laser that the nozzlemember 1 is formed practically free from any flaws such as minute cracksand scales. This contributes to improvement of net yield, and toimprovement of productivity.

Then, as shown in FIG. 6, a vibrating plate 11, which also acts as alid, is placed on the main surface 10 a, being the side upon which theconcave surfaces were prepared on the base plate 10. Thus, a space toact as an ink feed aperture 4 is formed between the third concavesurface 9 and the vibrating plate 11. A second space to act as an inkfeed channel 3 is formed between the second concave surface 8 and thevibrating plate 11. And, a third space to act as an ink chamber 2 isformed between the first concave surface 7 and the vibrating plate 11.These spaces communicate with each other and form, together with thenozzle member 1, a continuous passage for fluid.

An opening 12 is formed on part of the vibrating plate 11 opposite tothe third concave surface 9, and that opening communicates with part ofthe ink feed aperture 4. The vibrating plate 11 has thin grooves placedon its part so as to make its portion corresponding to the ink chamber 2ready to be displaced. A piezoelectric element 6 composed of laminatedpiezoelectric elements is placed on the portion of the vibrating plate11 which corresponds to the ink chamber 2. An ink feed pipe 13 isattached to an opening 12, and a supporting member 15 is attached to thepiezoelectrinc element 6 to complete the printer head.

In the above example, a base plate 10 has concavities formed accordingto a predetermined design by a processing means such as injectionmolding. Alternatively, the base plate 10, instead of being formed asabove, can be prepared by bonding a polymer film made of polyimide orthe like onto a metal plate. When such metal plate is used, it shouldhave a slightly different structure. As illustrated in FIG. 7, a polymerfilm 22 is bonded onto the main surface 21 a of a metal plate 21,whereby a first concave surface 27 to form part of an ink chamber, athird concave surface 29 to form part of an ink feed aperture, and anink feed channel 23 to connect between the first concave surface 27 andthe third concave surface 29 are produced, and the assembly acts as abase plate.

Such metal plate 21 may be made of, for example, stainless steel, andthe polymer film 22 may be made of polyimide or the like. If the film ismade of polyimide, it should have more wettability because a hole to actas a nozzle is bored through this film. Further, the film should beamenable to processing by abrasion with excimer laser. As such polyimidefilm, for example, Capton film™ available from Toray-Dupont can be used.Further the film should be preferably bonded onto the metal plate byhaving a coat type polyimide material with a low glass transitiontemperature inserted between itself and the metal plate. As suchpolyimide material, for example, Neoflex™ (glass transition temperaturebeing 200° C.) available from Mitsui Toatsu Chemicals can be used.

The polymer film 22 may also be made of polybenzimidazole having astructure as represented by the above Formula B. Such polymer film canbe produced after the polybenzimidazole has been processed into a filmor a very thin plate.

The base plate composed of a metal plate 21 and a polymer film 22 asdescribed above is as strong in resistance to chemical abrasion as theaforementioned base plate made of a single material.

Next, a liquid-repellent membrane 26 is formed upon the polymer film 22as illustrated in FIG. 8. The liquid-repellent membrane 26 canpreferably be formed with polybenzimidazole having a structure asrepresented by the above Formula A. Such polybenzimidazole preferablyhas a water absorbance of 4.0% or less when left in an atmosphere of 76%RH for 24 hours. To form the liquid-repellant membrane 26 made of suchpolybenzimidazole, the polybenzimidazole can be coated onto the polymerfilm.

Similar to that detailed above with respect to FIG. 4, an example of asuitable polybenzimidazole is a PBI matrix resin solution, such as NPBI™of cerazol painting grade available from Hoechst. This PBI matrix resinsolution, such as the NPBI™ provided by Hoechst, is a mixture thatresults after polybenzimidazole has been dispersed in anN,N-dimethylacetoamide solvent to give a 10 wt % resin solution, and isa liquid mass whose viscosity is 300±50CP.

The method to apply this mixture onto the polymer film 22 may includecoating by spraying, coating by dipping, and electrostatic coatingfollowed by baking at 300° C. or higher for 30 minutes or longer. Aliquid-repellent membrane 26, formed by this method, shows noadhesiveness in a wide temperature range from room temperature to 200°C. Alternatively, a polybenzimidazole material, which satisfies theabove requirements, is allowed to disperse in an N,N-dimethylacetoamidesolvent to give a 10 wt % resin solution. The resulting mixture may thenbe used as a coat on the polymer film 22.

When a different polybenzimidazole or polyimide material from the oneused for the liquid-repellent membrane 26 is used as a material for thepolymer film 22 as in this embodiment, a baking process requiringheating exceeding 300° C. or higher can be applied to the polymer film22, which would be impossible if the polymer film 22 were made ofpolysulfone or polyethersulfone.

Then, as illustrated in FIG. 9, a nozzle member 31 is formed with alaser processing machine which bores a hole penetrating from the bottomof the first concave surface 27 of the metal plate 21 through thepolymer film 22 and the liquid-repellant membrane 26. With the printingdevice of this example, a polybenzimidazole or polyimide material makingthe polymer film 22 and a second polybenzimidazole material making theliquid-repellent membrane 26 both allow processing by abrasion withexcimer laser, and thus, the nozzle member 31 can be formed throughprocessing by abrasion with excimer laser. Accordingly, the printingdevice of this embodiment, similar to the embodiment detailed above,allows simplified processing of nozzles, which contributes toimprovement of productivity. Moreover, polybenzimidazole and polyimidecan be so precisely processed by abrasion with excimer laser that thenozzle member 31 is formed practically free from any flaws such asminute cracks and scales. This reduces failures during processing,contributes to improvement of net yield, and contributes to improvementof productivity.

Then, similarly as described earlier with reference to FIG. 6, avibrating plate, an ink feed pipe, a piezoelectric element, a supportingmember, etc. are arranged appropriately to complete a printer head.

The printing device of this embodiment has the periphery of the nozzleorifice coated with liquid-repellent polybenzimidazole. This arrangementensures liquid-repellency at the periphery of the nozzle orifice, andthus allows stable ejection of ink and high-quality printing ofdocumentary images. Moreover, using the polybenzimidazole, the printingdevice of this embodiment can be processed by abrasion with excimerlaser, which will help simplify necessary processes and improveproductivity.

For the printing device of this embodiment, as described above, otherportions of the printer head (i.e. nozzle body and medium chambers),namely, the parts aside from the periphery of the nozzle orifice, can bemade of a second polybenzimidazole material or polyimide.

The present invention, in another embodiment, provides an improvedprinting device constructed to eject a mixture of ink and diluent. Thedetailed description will now focus on such an embodiment of the presentinvention. Of such printing devices, one where ink is applied to ametering nozzle and diluent to an ejecting nozzle will be referred to asa printing device based on “carrier jet” mode, or a “carrier-jetprinting device.”

The printing device of this embodiment has a printing head composed, asillustrated in FIG. 10, mainly of an orifice plate member 45 including afirst nozzle member 41, an ejecting medium chamber 42, an ejectingmedium feed channel 43, and an ejecting medium feed aperture 44, and asecond nozzle member 61, a metering medium chamber 62, a metering mediumfeed channel 63, and a metering medium feed aperture 64, and of firstand second piezoelectric elements 46 and 66 placed opposite to theejecting and metering medium chambers 42 and 62, respectively.Additionally, the printing device is also provided with a driving unitand a control unit (not shown).

Orifice plate 45 is composed of a base plate 50 provided with concavesurfaces forming part of chambers and nozzles, and a vibrating plate 51acting also as a lid covering such concave surfaces. The base plate 50has a first concave surface 47 which forms part of the ejecting mediumchamber 42, a second concave surface 48 shallower in its height than thefirst concave surface 47 and which forms part of the ejecting mediumfeed channel 43, and a third concave surface 49 deeper in its heightthan the second concave surface 48 and which forms part of the ejectingmedium feed aperture 44. The surfaces are prepared in such a way thattheir open sides intercommunicate with each other and are flush with amain surface 50 a. And, the surfaces have a passage formed from thefirst concave surface 47 up to a surface 50 b, or a surface opposite tothe surface 50 a, that is, a hole penetrating through the thickness ofthe base plate 50 to make a first nozzle member 41 therefrom.

The base plate 50 further has a fourth concave surface 67 which formspart of the metering medium chamber 62, a fifth concave surface 68shallower in its height than the fourth concave surface 67 and whichforms part of the metering medium feed channel 63, and a sixth concavesurface 69 deeper in its height than the fifth concave surface 68 andwhich forms part of the metering medium feed aperture 64. The surfacesare prepared in such a way that their open sides intercommunicate witheach other and are flush with the main surface 50 a . And, the surfaceshave a passage formed from the fourth concave surface 67 up to thesurface 50 b, or the surface opposite to the surface 50 a, that is, ahole penetrating through the thickness of the base plate 50 to make asecond nozzle member 61 therefrom.

The first nozzle member 41, as identified herein, consists of a nozzleorifice 41 a (outer portion) and a nozzle body 41 b (inner portion).Likewise, the second nozzle member 61, as referenced herein, consists ofa nozzle orifice 61 a (outer portion) and a nozzle body 61 b (innerportion). The first and second nozzle members 41 and 61, have theirorifices placed adjacent to each other on the back surface 50 b, andthus the ejecting medium and metering medium chambers 42 and 62, theejecting medium and metering medium feed channels 43 and 63, and theejecting medium and metering medium feed apertures 44 and 64 arearranged as if to surround the first and second nozzle members 41 and61.

The above-mentioned concave surfaces can take, for example, a form whosecross-section is shaped like a U. Whereas, the first and second nozzlemembers 41 and 61 may take a conical form whose circular, ellipsoid, orrectangular base tapers to a tiny orifice at the back surface 50 b toform a passage there.

A space formed between the third concave surface 49 and the vibratingplate 51 acts as an ejecting medium feed aperture 44. A second spaceformed between the second concave surface 48 and the vibrating plate 51acts as an ejecting medium feed channel 43. The third space formedbetween the first concave surface 47 and the vibrating plate 51 acts asan ejecting medium chamber 42. Each of these spaces communicate witheach other and form, together with the first nozzle member 41, acontinuous passage for fluid.

An opening 52 is formed on the part of the vibrating plate 51 oppositeto the third concave surface 49. To the opening 52 prepared at theejecting medium feed aperture 44 is attached an ejecting medium feedpipe 53 to provide ejecting medium from an ejecting medium feed tankoutside (not illustrated) to the printer head. Ejecting medium from theejecting medium feed tank outside is supplied through the ejectingmedium feed pipe 53 to the ejecting medium feed aperture 44. Theejecting medium then passes through the ejecting medium feed channel 43to the ejecting medium chamber 42 and to the first nozzle member 41.

On the other side of the printing head, a space formed between the sixthconcave surface 69 and the vibrating plate 51 acts as a metering mediumfeed aperture 64, a second space formed between the fifth concavesurface 68 and the vibrating plate 51 acts as a metering medium feedchannel 63, and a third space formed between the fourth concave surface67 and the vibrating plate 51 acts as a metering medium chamber 62. Eachof these spaces communicate with each other and form, together with thesecond nozzle member 61, a continuous passage for fluid.

An opening 72 is formed on the part of the vibrating plate 51 oppositeto the sixth concave surface 69. To the opening 72 prepared at themetering medium feed aperture 64 is fitted a metering medium feed pipe73 to provide metering medium from a metering medium feed tank outside(not illustrated) to the printer head. Metering medium from the meteringmedium feed tank outside is supplied through the metering medium feedpipe 73 to the metering medium feed aperture 64. The metering mediumthen passes through the metering medium feed channel 63 to the meteringmedium chamber 62 and to the second nozzle member 61. The vibratingplate 51 has thin grooves placed on its part so as to make its portionscorresponding to the ejecting and metering medium chambers 42 and 62ready to be displaced.

Laminated piezoelectric elements can be used as material appropriate forthe piezoelectric elements 46 and 66. This embodiment incorporates suchlaminated piezoelectric elements. A first piezoelectric element 46, asdescribed above, is placed on the part of the vibrating plate 51 whichcorresponds to the ejecting medium chamber 42 in such a manner that thelong axis of the piezoelectric element 46 contacts the vibrating plate51 at a right angle. The opposite end is fixed onto a supporting body55. The second piezoelectric element 66 has a similar construction. Itis placed on the part of the vibrating plate 51 which corresponds to themetering medium chamber 62, and its opposite end is fixed onto asupporting body 75.

The laminated piezoelectric elements composing the first and secondpressuring elements 46 and 66 extend/contract in the direction of theirlong axis under the influence of voltages applied. As being stabilizedat one end by supporting bodies 55 and 75, the piezoelectric elements 46and 66, during extension, exert a pressure onto the vibrating plate 51in the direction indicated with arrows P₁ and P₂ in FIG. 10. Thereby,ejecting medium 54 in the ejecting medium chamber 42 and metering medium74 in the metering medium chamber 62 are pressurized, and ejectingmedium 54 and metering medium 74 are pressed out from the nozzle members41 and 61, respectively. During this operation, no measurable counterflow of ejecting and metering medium towards ejecting medium andmetering medium feed apertures 54 and 74, respectively, will take place.This is because the ejecting and metering medium feed channels 43 and 63are narrower than the respective chambers 42 and 62.

For the printing device of this embodiment, the second piezoelectricelement 66 is first activated to exert a pressure on metering medium 74in the volume constant medium chamber 62 to press out a specific volumeof metering medium 74 from the second nozzle member 61 towards the firstnozzle member 41, thereby transferring the metering medium adjacent tothe orifice of the first nozzle member 41 to mix it with ejecting medium54 there. The volume of metering medium pressed out from the chamber 62can be varied according to the intensity or width of the voltage pulseapplied onto the second piezoelectric element 66.

Then, the first piezoelectric element 46 is activated to exert apressure on ejecting medium 54 in the ejecting medium chamber 42 toeject, together with the ejecting medium, the mixture comprisingmetering medium 74 and ejecting medium 54 stayed at the periphery of thenozzle orifice 41 a towards a medium to be printed upon (notillustrated). The tone of a given image can be reproduced after thevolume of metering medium 74 pressed out to be mixed with the ejectingmedium is adjusted to give a concentration corresponding to the tone.Both the ejecting medium 54 and metering medium 74 can be either ink ordiluent, and one takes ink then the other becomes diluent and viceversa. When ink is made the metering medium 74, the ink concentration ofa given dot can be varied by changing the volume of ink to be containedin that dot; whereas, when a diluent is the metering medium 74, the inkconcentration of a dot can be varied by changing the volume of thediluent to be contained in that dot.

The printing head of the printing device of this embodiment, as furtherindicated in the enlarged cross-section in FIG. 11, has aliquid-repellent membrane 56. Membrane 56 is formed at least on theperiphery of the first and second nozzle orifices 41 a and 61 a on theback surface 50 b. As illustrated in FIG. 10, the liquid-repellentmembrane 56 is formed all over the back surface 50 b .

The liquid-repellent membrane 56 can preferably be made ofpolybenzimidazole. A variety of chemicals can be used for thepolybenzimidazole. Preferably, chemicals having a structure asrepresented by the above Formula A are used. As described above, thepolybenzimidazole preferably have a water-absorbing property of 4.0% orless, when left in an atmosphere of 76% RH for 24 hours. An example of asuitable polybenzimidazole is a PBI matrix resin solution, such as NPBI™of cerazol painting grade available from Hoechst.

In the printing device of this embodiment, the base plate 50 canpreferably be made of polyimide or a different kind of polybenzimidazolefrom the above-described one of Formula A. A variety of chemicals areappropriate polybenzimidazole to be used as a material of the base plate50. Preferably, chemicals represented by the above Formula B are usedfor the base plate 50.

When the base plate 50 is made of polybenzimidazole as indicated above,it should be processed by a method at least comprising pressure molding,or by a method at least comprising injection molding. Suitable chemicalsthat may be used, for example, are U-60™ appropriate for pressuremolding and TU-60™ appropriate for injection molding, both availablefrom Hoechst.

When the base plate 50 is made of polybenzimidazole as described above,the liquid-repellent membrane 56 may be formed of a substancepolymerizing at 150° C. or higher, as well as of polybenzimidazole. Forexample, polyimide polymers into which a fluorine polymer has beendispersed may be used as the liquid-repellant membrane 56. In anembodiment, the fluorine polymer is a copolymer of tetrafluoroethyleneand hexafluoropropylene.

This printing device, in an embodiment, has the periphery of the firstand second nozzle orifices 41 a and 61 a on the side of the printer headupon which the orifices are formed coated with liquid-repellentpolybenzimidazole. This arrangement ensures liquid-repellency of atleast the periphery of the first and second nozzle orifices 41 a and 61a. With this example, therefore, ink and diluent are completelyseparated from each other during stand-by or before they are mixed. Themixing ratio of ink and diluent can be precisely adjusted dot by dot.Thus, the ink concentration can be accurately controlled in accordancewith the tone of a given image to be reproduced. Accordingly, thisprinting device promotes high-resolution reproduction of documentaryimages. Moreover, the printing device of this embodiment, similarly tothe above-described devices where only ink is ejected, allows stableejection of ejecting medium, which further helps improve high-resolutionreproduction of documentary images.

The present invention also provides a method for manufacturing suchprinting device having ejecting and metering chambers. The detaileddescription will now focus on a method for producing such a printerhead. As illustrated in FIG. 12, a base plate 50 is so processed as togive a first concave surface 47, a second concave surface 48 and a thirdconcave surface 49 which open towards a main surface 50 a. The firstconcave section 47, second concave section 48 and third concave section49 are so processed as to give a continuous passage, and theirconfiguration is as described above. A fourth concave surface 67, afifth concave surface 68 and a sixth concave surface 69 are also formedto give a continuous passage. Their configuration is as described above.The method appropriate for processing the base plate 50 includesinjection molding or pressure molding. As indicated above, materialsthat may be utilized the base plate include polybenzimidazole andpolyimide. However, the preferred material should include a differentpolybenzimidazole or polyimide material from the one used for theliquid-repellent membrane 56.

In an embodiment, polybenzimidazole or polyimide are used. Thepolybenzimidazole used for the base plate 50 should preferably have astructure as represented by the above Formula B. Suitable chemicals thatmay be used, as detailed previously, include U-60™ appropriate forpressure molding and TU-60™ appropriate for injection molding, bothavailable from Hoechst. Such polybenzimidazole has a good wettability,is suitable for processing by abrasion with excimer laser, allows easyprocessing of nozzles, and prevents practically all entry of air bubblesinto the nozzles. Any polyimide may be used for the base plate 50 aslong as it has such a grade as to be applied for injection molding. Anexample of a suitable chemical is polyimide available from Mitsui ToatsuChemicals.

Then, as illustrated in FIG. 13, a liquid-repellent membrane 56 isformed on a back surface 50 b or the surface opposite to the mainsurface 50 a of the base plate 50. The liquid-repellent membrane 56 canpreferably be made of such polybenzimidazole as has a structure asrepresented by the above Formula A. Such polybenzimidazole should alsopreferably have a water-absorbing property of 4.0% or less, when left inan atmosphere of 76% RH for 24 hours.

As previously detailed above, an example of a suitable polybenzimidazoleis a PBI matrix resin solution, such as NPB™ of cerazol painting gradeavailable from Hoechst. This PBI matrix resin solution is a mixture thatresults after polybenzimidazole has been dispersed in anN,N-dimethylacetoamide solvent to give a 10 wt % resin solution, and isa liquid mass whose viscosity is 300±50CP. The method to apply thismixture onto the base plate 50 may include coating by spraying, coatingby dipping, and electrostatic coating followed by baking at 300° C. orhigher for 30 minutes or longer. A liquid-repellent membrane, formed bythe above method, shows no adhesiveness in a wide temperature range fromroom temperature to 200° C. Alternatively, a polybenzimidazole material,which satisfies the above requirements, is allowed to disperse in anN,N-dimethylacetoamide solvent to give a 10 wt % resin solution. Theresulting mixture may be coated on the base plate 50 in the same way asabove.

When a different polybenzimidazole or polyimide material from the oneused for the liquid-repellent membrane 56 is used as a material for thebase plate 50 as in this embodiment, a baking process requiring heatingexceeding 300° C. or higher can be applied to the base plate. Such aprocess would be impossible if the base plate were made of polysulfoneor polyethersulfone.

Then, as illustrated in FIG. 14, a nozzle member 41 is formed with alaser processing machine which bores a hole penetrating from the bottomof the first concave surface 47 of the base plate 50 through the baseplate 50 and the liquid-repellent membrane 56. In addition, anothernozzle member 61 is formed with a laser processing machine which bores ahole penetrating from the bottom of the fourth concave surface 67 of thebase plate 50 through the base plate 50 and the liquid- repellentmembrane 56. With the printing device of this embodiment, apolybenzimidazole or polyimide material making the base plate 50 and asecond polybenzimidazole material making the liquid-repellent membrane56 both allow processing by abrasion with excimer laser, and thus, thefirst and second nozzle members 41 and 61 can be formed throughprocessing by abrasion with excimer laser. Accordingly, the printingdevice of this embodiment, as with other embodiments, allows simplifiedprocessing of nozzles, which contributes to improvement of productivity.Moreover, the polybenzimidazole and polyimide can be so preciselyprocessed by abrasion with excimer laser that the first and secondnozzle members 41 and 61 are formed practically free from any flaws suchas minute cracks and scales.

This reduces failures during processing, contributes to improvement ofnet yield, and contributes to improvement of productivity.

Then, as shown in FIG. 15, a vibrating plate 51 to act also as a lid isplaced on the main surface 50 a. Thus, a space formed between the thirdconcave surface 49 and the vibrating plate 51 creates an ejecting mediumfeed aperture 44, a second space formed between the second concavesurface 48 and the vibrating plate 51 creates an ejecting medium feedchannel 43, and a third space formed between the first concave surface47 and the vibrating plate 51 creates an ejecting medium chamber 42.These spaces communicate with each other and form, together with thefirst nozzle member 41, a continuous passage for fluid. An opening 52 isformed on part of the vibrating plate 51 opposite to the third concavesurface 49, and that opening communicates with part of the ejectingmedium feed aperture 44.

Additionally, the vibrating plate 51 is arranged such that a spaceformed between the sixth concave surface 69 and the vibrating plate 51creates a metering medium feed aperture 61, a second space formedbetween the fifth concave surface 68 and the vibrating plate 51 createsa metering medium feed channel 63, and a third space formed between thefirst concave surface 67 and the vibrating plate 51 creates a meteringmedium chamber 62. These spaces communicate with each other and form,together with the second nozzle member 61, a continuous passage forfluid. An opening 72 is formed on the part of the vibrating plate 51opposite to the sixth concave surface 69, and that opening communicateswith part of the metering medium feed aperture 64. The vibrating plate51 has thin grooves placed on its part so as to make its portionscorresponding to the ejecting and metering chambers 42 and 62 ready tobe displaced.

A piezoelectric element 46 composed of laminated piezoelectric elementsis placed on the part of vibrating plate 51 corresponding to theejecting medium chamber 42. Likewise, another piezoelectric element 66composed of laminated piezoelectric elements is placed on the part ofthe vibrating plate 51 corresponding to the metering medium chamber 62.These piezoelectric elements 46 and 66 are supported by supportingbodies 55 and 75. Lastly, an ejecting medium feed pipe 53 is connectedto the opening 52 and a metering medium feed pipe 73 to the opening 72,thereby to complete a printer head.

In the above embodiment, the base plate 50 has concavities formedaccording to a predetermined design through a processing means such asinjection molding. Alternatively, the base plate 50, instead of beingformed as above, can be prepared by bonding a polymer film made ofpolyimide or the like onto a metal plate. When such metal plate is used,it should have a slightly different structure. As illustrated in FIG.16, a polymer film 82 is bonded onto the main surface 81 a of a metalplate 81, whereby a first concave surface 87 to form part of an ejectingmedium chamber, a third concave surface 89 to form part of an ejectingmedium feed aperture, and an ink feed channel 83 to connect between thefirst concave surface 87 and the third concave surface 89 are produced.In addition, a fourth concave surface 97 to form part of a meteringmedium chamber, a sixth concave surface 99 to form part of a meteringmedium feed aperture, and a metering medium feed channel 93 to connectbetween the fourth concave surface 97 and the sixth concave surface 99are prepared. This assembly acts as a base plate.

Such metal plate 81 may be made of, for example, stainless steel, andthe polymer film 82 may be made of polyimide or the like. If the film ismade of polyimide, it should have more wettability because a hole to actas a nozzle is bored through this film. Further, the film should beamenable to processing by abrasion with excimer laser. As such polyimidefilm, for example, Capton film™ available from Toray-Dupont can be used.Further the film should be preferably bonded onto the metal plate byhaving a coating type polyimide material with a low glass transitiontemperature inserted between itself and the metal plate. As suchpolyimide material, for example, Neoflex™ (glass transition temperaturebeing 200° C.) available from Mitsui Toatsu Chemicals can be used.

The polymer film 82 may be also be made of polybenzimidazole having astructure as represented by the above Formula B. Such polymer film canbe produced after the polybenzimidazole has been processed into a filmor a very thin plate.

The base plate composed of a metal plate 81 and a polymer film 82 havinga construction as described above is as strong in resistance to chemicalabrasion as the aforementioned base plate made of a single material.

Next, as illustrated in FIG. 17, a liquid-repellent membrane 84 isformed upon the polymer film 82. The liquid-repellent membrane 84 canpreferably be made of such polybenzimidazole having a structure asrepresented by the above Formula A. Such polybenzimidazole preferablyhas a water-absorbing property of 4.0% or less, when left in anatmosphere of 76% RH for 24 hours. To form the liquid-repellant membrane84 made of such polybenzimidazole, the polybenzimidazole can be coatedonto the polymer film.

Similar to that detailed above with respect to FIG. 8, an example of asuitable polybenzimidazole is a PBI matrix resin solution, such as NPB™of cerazol painting grade available from Hoechst. This PBI matrix resinsolution, such as the NPBI™ provided by Hoechst, is a mixture thatresults after polybenzimidazole has been dispersed in anN,N-dimethylacetoamide solvent to give a 10 wt % resin solution, and isa liquid mass whose viscosity is 300±50CP.

The method to apply this mixture onto the polymer film 82 may includecoating by spraying, coating by dipping, and electrostatic coatingfollowed by baking at 300° C. or higher for 30 minutes or longer. Aliquid-repellent membrane 84, formed by this method, shows noadhesiveness in a wide temperature range from room temperature to 200°C. Alternatively, a polybenzimidazole material, which satisfies theabove requirements, is allowed to disperse in an N,N-dimethylacetoamidesolvent to give a 10 wt % resin solution. The resulting mixture may thenbe used as a coat on the polymer film 84 in the same way as above.

When a different polybenzimidazole or polyimide material from the oneused for the liquid-repellent membrane 84 is used as a material for thepolymer film 82 as in this embodiment, a baking process requiringheating exceeding 300° C. or higher can be applied to the polymer film82, which would be impossible if the polymer film 82 were made ofpolysulfone or polyethersulfone.

Then, as illustrated in FIG. 18, a first nozzle member 85 is formed witha laser processing machine which bores a hole penetrating from thebottom of the first concave surface 87 of the metal plate 81 through thepolymer film 82 and the liquid-repellant membrane 84. In addition, asecond nozzle member 86 is formed with a laser processing machine whichbores a hole penetrating from the bottom of the fourth concave surface97 of the metal plate 81 through the polymer film 82 and the liquidrepellant membrane 84.

With the printing device of this embodiment, a polybenzimidazole orpolyimide material making the polymer film 82 and a secondpolybenzimidazole material making the liquid-repellent membrane 84 bothallow processing by abrasion with excimer laser, and thus, the first andsecond nozzles members 85 and 86 can be formed through processing byabrasion with excimer laser. Accordingly, the printing device of thisembodiment, similar to the embodiments detailed above, allows simplifiedprocessing of nozzles, which contributes to improvement of productivity.Moreover, polybenzimidazole and polyimide can be so precisely processedby abrasion with excimer laser that the first and second nozzle members85 and 86 are formed practically free from any flaws such as minutecracks and scales. This reduces failures during processing, contributesto improvement of net yield, and contributes to improvement ofproductivity.

Then, similarly as described earlier, a vibrating plate, an ejectingmedium feed pipe, a metering feed pipe, piezoelectric elements, etc. arearranged appropriately to complete a printer head.

This printing device, in an embodiment, has the periphery of the nozzleorifices coated with liquid-repellent polybenzimidazole. This ensuresthereby liquid-repellency of at least the periphery of the nozzleorifices. With this embodiment therefore, ink and diluent are completelyseparated from each other during stand-by or before they are mixed. Themixing ratio of ink and diluent can be precisely adjusted dot by dot.Thus, the ink concentration can be accurately controlled in accordancewith the tone of a given image to be reproduced. Accordingly, thisprinting device can allow high-resolution printing of documentaryimages. Moreover, the printing device of this embodiment ensures stableejection of ejecting medium, which alone may help improvehigh-resolution reproduction of documentary images.

With the printing device of this embodiment, above polybenzimidazoleallows processing by abrasion with excimer laser, and thus, the nozzlescan be formed by abrasion with excimer laser. Alternatively, theprinting devices can be prepared by abrasion with excimer laser combinedwith pressure molding and injection molding. Accordingly, the printingdevice of this embodiment can be produced by simple procedures, whichwill result in improved productivity.

The method by which to manufacture the above described printing deviceswhere only ink is ejected may include, for example, the followingmethods. The description will first focus on an example in which anozzle is formed by abrasion with excimer laser combined with pressuremolding. First, as is illustrated in FIG. 19, a plate base material 101,which is composed of polybenzimidazole amenable to processing byabrasion with excimer laser and having a structure as represented by theabove Formula B, such as U-60™ available from Hoechst, is prepared.

Then, this base material 101 is put into a pressure mold die forpressure molding. This results in the formation of a base plate 105which has, as illustrated in FIG. 20, a first concave surface 102, asecond concave surface 103, and a third concave surface 104 formed suchthat their mouths open towards the main surface 105 a. These concavesurfaces communicate with each other and their configuration is asdescribed above. In this example, during the pressure molding, a nozzleconduit 106 is formed as a blind hole in the substance of the base plate105 from the bottom of the first concave surface 102. Then, asillustrated in FIG. 21, a liquid-repellent membrane 107 is formed uponthe back surface 105 b or a surface opposite to the main surface 105 aof the base plate 105.

In the above examples, the liquid-repellent membrane is made ofpolybenzimidazole. When the base plate 105 as in this embodiment is madeof polybenzimidazole, such as U-60™ by Hoechst, the range of materialsto be used for the liquid-repellent membrane 107 will broaden greatly.This is because such a commercial polybenzimidazole has a thermalresistance exceeding 400° C.

Specifically, the material to be used for the liquid-repellent membrane107 can include materials which polymerize at 150° C. or higher, orpolyimide polymers in which a fluorine polymer has been dispersed.Examples appropriate for the liquid-repellent membrane 107 may includepolybenzimidazole, Yupicoat FS-100L™ or a polyimide overcoating inkprovided by Ube Industries, and Yupifine FP-100™ or a polyimide coatingmaterial by the same manufacturer, whose water absorbance is 0.4% orless. Further, it may include modified polytetrafluoroethylene coating958-207™ manufactured by DuPont, or a compound which results bydispersing polytetrafluoroethylene particles into a polyimide material.These compounds are all particularly amenable to processing by abrasionwith excimer laser.

The liquid-repellent membrane 107 may be so processed as to give athickness of 10-30 μm. The membrane should preferably have a thicknessof 5 μm or more, because then it will scarcely develop pin holes.

Provided that the construction of the nozzle does not require muchprecision, or in other words, that the nozzle may be inflicted with moreor less minor flaws, or that the liquid-repellent membrane may have athickness of 5 μm or less, a polytetrafluoroethylene can be used as amaterial of the liquid-repellent membrane.

Then, as illustrated in FIG. 22, a nozzle orifice taper 108 is formedwith a laser processing machine which bores a hole penetrating from thebottom of the nozzle conduit 106 of the base plate 105 through the baseplate 105 and the liquid-repellent membrane 107. With the printingdevice of this embodiment, a polybenzimidazole material making the baseplate 105 and a second polybenzimidazole material making theliquid-repellent membrane 107 both allow processing by abrasion withexcimer laser, and thus, the nozzle orifice taper 180 can be formed byabrasion with excimer laser.

Then, a vibrating plate is applied in the same manner as described aboveto complete the present printing device. In this example, the range ofmaterials to be used for bonding will broaden greatly, because thetemperature of about 200° C. developed during the process necessary forbonding of the vibrating plate does not pose any problem. Formation ofnozzles by this method, therefore, will lead to a lowering of productioncost and improved productivity, because processing by abrasion withexcimer laser can be minimized.

Next, the description will focus on an example in which a nozzle isformed by abrasion with excimer laser combined with injection molding.First, a polybenzimidazole material amenable to processing by abrasionwith excimer laser and having a structure as represented by the aboveFormula B, such as TU-60™ by Hoechst, is prepared. This material is putinto an injection mold die (not illustrated) for injection molding.

As a result, this base material gives a base plate 105 which has, asillustrated in FIG. 20, a first concave surface 102, a second concavesurface 103, and a third concave surface 104 formed such that theirmouths open towards the main surface 105 a. These concave surfaces, inthe same manner as above, communicate with each other and theirconfiguration is the same as above. In this example, during theinjection molding, a nozzle conduit 106 is formed as a blind hole in thesubstance of the base plate 105 from the bottom of the first concavesurface 102. Then, as illustrated in FIG. 21, a liquid-repellentmembrane 107 is formed upon the back surface 105 b or a surface oppositeto the main surface 105 a of the base plate 105.

As indicated above, in the above examples, the liquid-repellent membraneis made of polybenzimidazole. When the base plate 105 in this embodimentis made of polybenzimidazole, such as TU-60™ available from Hoechst, therange of materials to be used for the liquid-repellent membrane 107 willbroaden greatly, because such a commercial polybenzimidazole has athermal resistance exceeding 250° C.

Specifically, in this embodiment, the material to be used for theliquid-repellent membrane 107 can include materials which polymerize at150° C. or higher, or polyimide polymers in which a fluorine polymer hasbeen dispersed. Examples appropriate for the liquid-repellent membrane107 may include, polybenzimidazole, Yupicoat FS-100L™ or a polyimideovercoating ink provided by Ube Industries, and Yupifine FP-100™ or apolyimide coating material by the same manufacturer, both of which havea water absorbance of less than 0.4% or less. Further, it may includemodified polytetrafluoroethylene coating 958-207™ by DuPont, or acompound which results by dispersing polytetrafluoroethylene particlesinto a polyimide material. These compounds are all particularly amenableto processing by abrasion with excimer laser.

Of the materials mentioned above, polybenzimidazole requires apolymerization process developing a temperature of 300° C. or higher.Even the process requiring such a high temperature, however, will notinflict any noticeable damage to the base plate 105, because thepolybenzimidazole in question is very close in its basic composition tothe polybenzimidazole composing the base plate 105. Further, thecompound which results after having dispersed polytetrafluoroethyleneparticles into a polyimide material requires a polymerization processinvolving heating to a temperature of about 340° C. This process willnot inflict damage to the base plate 105 either, because this processrequires only a short period, and the temperature the base plate will beexposed to during the process will not exceed the thermal resistancelimit of the plate by 100° C. or higher.

The liquid-repellent membrane 107 may be so processed as to give, forexample, a thickness of 10-30 μm. The membrane should preferably have athickness of 5 μm or more, because then it will scarcely develop pinholes.

Provided that the construction of the nozzle does not require muchprecision, or in other words, that the nozzle may be inflicted more orless with minor flaws, or that the liquid-repellent membrane may have athickness of 5 μm or less, a polytetrafluoroethylene can be used as amaterial of the liquid-repellent membrane.

Then, as illustrated in FIG. 22, a nozzle orifice taper 108 is formedwith a laser processing machine which bores a hole penetrating from thebottom of the nozzle conduit 106 of the base plate 105 through the baseplate 105 and the liquid-repellent membrane 107. With the printingdevice of this example, a polybenzimidazole material making the baseplate 105 and a material making the liquid-repellent membrane 107 bothallow processing by abrasion with excimer laser, and thus, the nozzleorifice taper 180 can be formed by abrasion with excimer laser.

Then, a vibrating plate is applied in the same manner as described aboveto complete the present printing device. In this example, the range ofmaterials to be used for bonding will broaden greatly, because the baseplate 105 is made of a polybenzimidazole material having a high thermalresistance, and the temperature of about 200° C. developed during theprocess necessary for bonding of the vibrating plate does not pose anyproblem. Formation of nozzles by this method, therefore, will lead to alowering of production cost and improved productivity, becauseprocessing by abrasion with excimer laser can be minimized.

The method by which to manufacture the above described printing deviceswhere ink and diluent are ejected while being mixed together mayinclude, for example, the following methods. The description will firstfocus on an example in which nozzles are formed by abrasion with excimerlaser combined with pressure molding. As is illustrated in FIG. 23, abase plate material 111 which is composed of polybenzimidazole amenableto processing by abrasion with excimer laser and having a structure asrepresented by the above Formula B, such as U-60™ by Hoechst, is firstprepared.

Then, this base material 111 is put into a pressure mold die forpressure molding. This results in the formation of a base plate 115which has, as illustrated in FIG. 24, a first concave surface 112, asecond concave surface 113, and a third concave surface 114 formed suchthat their mouths open towards the main surface 115 a. Likewise, thepressure mold creates a fourth concave surface 122, a fifth concavesurface 123, and a sixth concave surface 124 formed such that theirmouths open towards the main surface 115 a. Those concave surfacescommunicate with each other and their configuration is as describedabove. In this example, during the pressure molding, a nozzle conduit116 is formed as a blind hole in the substance of the base plate 115from the bottom of the first concave surface 112, while a second nozzleconduit 126 is formed as a blind hole obliquely directed to thethickness of the base plate 115 from the bottom of the fourth concavesurface 122. Then, as illustrated in FIG. 25, a liquid-repellentmembrane 117 is formed upon the back surface 115 b or a surface oppositeto the main surface 115 a of the base plate 115.

As previously described with respect to the other embodiments, theliquid-repellent membrane is made of polybenzimidazole. However, whenthe base plate 115 in this embodiment is made of polybenzimidazole, suchas U-60™ by Hoechst, the range of materials to be used for theliquid-repellent membrane 117 will broaden greatly, because such acommercial polybenzimidazole has a thermal resistance exceeding 400° C.

Specifically, the material to be used for the liquid-repellent membrane117 can include materials which polymerize at 150° C. or higher, orpolyimide polymers in which a fluorine polymer has been dispersed.Examples appropriate for the liquid-repellent membrane 117 may includepolybenzimidazole, Yupicoat FS-100™ or a polyimide overcoating inkprovided by Ube Industries, and Yupifine FP-100™ or a polyimide coatingmaterial by the same manufacturer, both of which have a water absorbanceof less than 0.4% or less. Further, it may include modifiedpolytetrafluoroethylene coating 958-207™ by DuPont, or a compound whichresults by dispersing polytetrafluoroethylene particles into a polyimidematerial. These compounds are all particularly amenable to processing byabrasion with excimer laser.

The liquid-repellent membrane 117 may be so processed as to give, forexample, a thickness of 10-30 μm. The membrane should preferably have athickness of 5 μm or more, because then it will scarcely develop pinholes.

Provided that the construction of the nozzle does not require muchprecision, or in other words, that the nozzle may be inflicted with moreminor flaws, or that the liquid-repellent membrane may have a thicknessof 5 μm or less, a polytetrafluoroethylene can be used as a material ofthe liquid-repellent membrane.

Then, as illustrated in FIG. 26, with a laser processing machine a firstnozzle orifice taper 118 is formed as a hole penetrating from the bottomof the first nozzle conduit 116 of the base plate 115 through the baseplate 115 and the liquid-repellent membrane 117. Likewise, a secondnozzle orifice taper 128 is formed as a hole from the bottom of thesecond nozzle conduit 126 obliquely directed to the thickness of thebase plate 115 and penetrating the base plate 115 and theliquid-repellent membrane 117. With the printing device of thisembodiment, a polybenzimidazole material making the base plate 105 and amaterial making the liquid-repellent membrane 107 both allow processingby abrasion with excimer laser, and thus, the nozzle orifice tapers 118and 128 can be formed by abrasion with excimer laser.

Then, a vibrating plate is applied in the same manner as described aboveto complete the present printing device. In this embodiment, the rangeof materials to be used for bonding will broaden greatly, because thebase plate 115 is made of a polybenzimidazole material having a highthermal resistance, and the temperature about 200° C. developed duringthe process necessary for bonding of the vibrating plate does not poseany problem. Formation of nozzles by this method, therefore, will leadto a lowering of production cost and improved productivity, becauseprocessing by abrasion with excimer laser can be minimized.

Next, the description will focus on an example in which nozzles areformed by abrasion with excimer laser combined with injection molding.First, a polybenzimidazole material amenable to processing by abrasionwith excimer laser and having a structure as represented by the aboveFormula B, such as TU-60™ by Hoechst is prepared. This material is putinto an injection mold die (not illustrated) for injection molding.

As a result, this base material gives a base plate 115 which has, asillustrated in FIG. 24, a first concave surface 112, a second concavesurface 113, and a third concave surface 114 formed such that theirmouths open towards the main surface 115 a. Additionally, the injectionmold creates a fourth concave surface 122, a fifth concave surface 123,and a sixth concave surface 124 also formed such that their mouths opentowards the main surface 115 a. These concave surfaces, in the samemanner as above, communicate with each other and their configuration isthe same as above. In this embodiment, during the pressure molding, anozzle conduit 116 is formed as a blind hole in the substance of thebase plate 115 from the bottom of the first concave surface 112, while asecond nozzle conduit 126 is formed as a blind hole obliquely directedto the thickness of the base plate 115 from the bottom of the fourthconcave surface 122. Then, as illustrated in FIG. 25, a liquid-repellentmembrane 117 is formed upon the back surface 115 b or a surface oppositeto the main surface 115 a of the base plate 115.

In this embodiment, the liquid-repellent membrane is made ofpolybenzimidazole. However, when the base plate 115 in this embodimentis made of polybenzimidazole, such as TU-60™ by Hoechst, the range ofmaterials to be used for the liquid-repellent membrane 117 will broadengreatly, because that polybenzimidazole has a thermal resistanceexceeding 250° C.

Specifically, the material to be used for the liquid-repellent membrane117 can include materials which polymerize at 150° C. or higher, orpolyimide polymers in which a fluorine polymer has been dispersed.Examples appropriate for the liquid-repellent membrane 117 may include,polybenzimidazole, Yupicoat FS-100L™ or a polyimide overcoating inkprovided by Ube Industries, and Yupifine FP-100™ or a polyimide coatingmaterial by the same manufacturer, both of which have a water absorbanceof less than 0.4% . Further, it may include modifiedpolytetrafluoroethylene coating 958-207™ by DuPont, or a compound whichresults by dispersing polytetrafluoroethylene particles into a polyimidematerial. These compounds are all particularly amenable to processing byabrasion with excimer laser.

Of the materials mentioned above, the polybenzimidazole requires apolymerization process developing a temperature of 300° C. or higher.Even the process requiring such a high temperature, however, will notinflict any noticeable damage to the base plate 115, because thepolybenzimidazole in question is very close in its basic composition tothe polybenzimidazole composing the base plate 115. Further, thecompound which results after having dispersed polytetrafluoroethyleneparticles into a polyimide material requires a polymerization processinvolving heating to a temperature about 340° C. This process will notinflict damage to the base plate 115 neither, because this processrequires only a short period, and the temperature to which the baseplate will be exposed during the process will not exceed the thermalresistance limit of the plate by 100° C. or higher.

The liquid-repellent membrane 117 may be so processed as to give, forexample, a thickness of 10-30 μm. The membrane should preferably have athickness of 5 μm or more, because then it will scarcely develop pinholes.

Provided that the construction of the nozzle does not require muchprecision, or in other words, that the nozzle may be inflicted with moreor less minor flaws, or that the liquid-repellent membrane may have athickness of 5 μm or less, PTFE (a tetrafluoroethylene resin) can beused as a material of the liquid-repellent membrane.

Then, as illustrated in FIG. 26, with a laser processing machine a firstnozzle orifice taper 118 is formed as a hole penetrating from the bottomof the first nozzle conduit 116 of the base plate 115 through the baseplate 115 and the liquid-repellent membrane 117. Likewise, a secondnozzle orifice taper 128 is formed as a hole from the bottom of thesecond nozzle conduit 126 obliquely directed to the thickness of thebase plate 115 and penetrating the base plate 115 and theliquid-repellent membrane 117. With the printing device of thisembodiment, a polybenzimidazole material making the base plate 105 and amaterial making the liquid-repellent membrane 117 both allow processingby abrasion with excimer laser, and thus, the nozzle orifice tapers 118and 128 can be formed by abrasion with excimer laser.

Then, a vibrating plate is applied in the same manner as described aboveto complete the present printing device. In this embodiment, the rangeof materials to be used for bonding will broaden greatly, because thebase plate 115 is made of a polybenzimidazole material having a highthermal resistance, and the temperature of about 200° C. developedduring the process necessary for bonding of the vibrating plate does notpose any problem. Formation of nozzles by this method, therefore, willlead to a lowering of production cost and improved productivity, becauseprocessing by abrasion with excimer laser can be minimized.

Of course, with the printing devices described above which have beenproduced by the method comprising abrasion with excimer laser combinedwith pressure molding or injection molding, the same effects can beobtained as those characteristic to the printing devices mentionedearlier.

Further, in this invention, the liquid-repellent membranes 16, 26, 56,84, 107 and 117 shown in FIGS. 2, 8, 11, 17, 21 and 25, respectively,can be constituted by a polyimide polymer in which a fluorine polymer isdispersed. The fluorine polymer may include various chemicals, butpreferably includes a copolymer of tetrafluoroethylene andhexafluoroethylene or the like which have a structure as represented bythe following Formula C.

where m and n are mole percentages, m being a positive integer from 1 to99 and n being a positive integer from 99 to 1. Preferably, the fluorinepolymer has a molecular weight of about 5,000 to 500,000.

The polyimide polymer may have a property to polymerize when heated to300° C. or higher. An example of a suitable fluorine polymer that meetssuch requirements as above is Teflon® coating 958-207 available fromDuPont.

Moreover, the polyimide polymer, besides those mentioned above, mayinclude various chemicals including aromatic polyimides. It may includefurther the compounds which have a structure as represented by thefollowing Formula D and Formula E.

where n represents a positive integer, and R is a divalent bridgingunit. For example, R can be any of the following: O, CO, CH₂, C₂ H₄.

where D represents a positive integer. The polyimide polymers ofFormulas D and E preferably have a molecular weight of about 5,000 to1,000,000.

Such Polyimide polymers preferably have a water absorbance of 0.4% orless when kept in water of 23° C. for 24 hours. Such polyimide polymersmay further have a property to polymerize when heated to 180° C. orlower.

In an embodiment, the polyimide polymer may include Polyimidesiloxane.The polyimidesiloxane preferably has a structure as represented by thefollowing Formula F and Formula G.

where k, l, m and n represent positive integers, R is a divalentbridging unit, and R₁ can be CH₂, (CH₂)₂, (CH₂)₃, (CH₂)₄, or (CH₂)₅; andR₂ can be CH₃, C₂H₅, or C₃H₇. The polyimidesiloxane preferably has amolecular weight of about 5,000 to 1,000,000.

The polyimidesiloxane is preferably a compound which results afterhaving part of its aromatic hydrocarbon component substituted bysiloxane, and has a 3-25 weight % of Si with respect to polyimide. Anexample of a polyimide polymer that satisfies these requirements mayinclude Yupicoat FS-100L™ and Yupifine FP-100™ ,both available from UbeIndustries. Still further, the polyimide polymer, besides above, mayinclude compounds which have a structure as represented by the followingFormula H:

where m represents a positive integer. An example of such a polyimidepolymer is a coating type polyimide PIQ640™ available from HitachiChemical. The polyimide polymer of Formula H preferably has a molecularweight of about 5,000 to 500,000.

In an embodiment, the printing device of this invention has at least theperiphery of the nozzle orifice made of a polyimide polymer in which afluorine polymer is dispersed. This arrangement ensuresliquid-repellency around the periphery of nozzle orifice. In addition,because the polyimide polymer can be appropriately processed by abrasionwith excimer laser, the printing device of this invention allows thenozzle to be formed by abrasion with an excimer laser.

As previously mentioned, for the printing device of this invention,other parts than the nozzle member of the printer head, namely, theparts excluding the periphery of the nozzle orifice which is made of apolyimide polymer with a dispersion of a fluorine polymer, are made of asecond polyimide polymer with a dispersion of a fluorine polymer.Because these substances are highly resistant to heating, the peripheryof the nozzle opening can be made of a material which polymerizes at aconsiderably high temperature of about 300° C. Because such materialsare necessarily suitable for abrasion with excimer laser, the printingdevice of this invention will thus allow the nozzle of the printing headto be processed by abrasion with excimer laser.

The fluorine polymer and polyimide polymer used for the liquid-repellentmembranes may include the compounds as described above. For example,Teflon coating 958-207 by DuPont or a copolymer of tetrafluoroethyleneand hexafluoropropylene can be used as a polyimide polymer with afluorine polymer dispersed within.

The method to apply Teflon coating 958-207 by DuPont onto the base platemay include coating by spraying, coating by dipping, and a procedurewherein a coat of 10-30 μm thickness is formed on the plate, and theassembly is dried at about 150° C., and baked at 300° C. or higher (forexample 340° C.). As a result, a liquid-repellent membrane with aliquid-repellency appropriate for the printer head is formed. Moreover,because a different polyimide polymer from the one used for theformation of the liquid-repellent membrane is used as a material for theorifice plate, a baking process requiring heating exceeding 300° C. orhigher can be applied to the orifice plate, which would be impossible ifthe orifice plate were made of polysulfone or polyethersulfone.

By way of example, and not limitation, experimental results conductedfor the present invention will be set forth.

To check the effects of the polyimide described above, the followingexperiments were performed. A coat appropriate for the printing deviceof this invention was prepared. The coat consisted of Teflon coating958-207 available from DuPont or a polyimide polymer in which acopolymer resin of tetrafluoroethylene and hexafluoropropylene had beendispersed. A second coat was prepared which consisted of Teflon coating954-101 available from DuPont or an epoxy polymer in which a copolymerresin of tetrafluoroethylene and hexafluoropropylene had been dispersed.The two coats were subjected to abrasion with an excimer laser, andtheir amenability to laser processing and liquid-repellency wereevaluated.

First, test samples were prepared. Teflon coating 958-207 available fromDuPont was spread to a coat of 10-15 μm thickness, which was then driedat 150° C., and baked at 340° C. to produce a sample coat #1. As acomparison, Teflon coating 958-207 by DuPont was spread to a coat of10-15 μm thickness, which was then dried at 150° C. to produce a samplecoat #2. As a further comparison, Teflon coating 954-101 by DuPont wasspread to a coat of 10-15 μm, which was then dried at 240-250° C. toproduce a sample coat #3.

Abrasion with an excimer laser was applied to these samples, and theiramenability to abrasion with excimer laser and liquid-repellency wereevaluated. The amenability to abrasion was evaluated as follows. Twoholes were bored through the thickness of the coat by abrasion with anexcimer laser: one had an axis parallel to the thickness of the coat,and the other has an axis oblique to the same thickness. The shape ofthe hole and presence of minor flaws were checked. The liquid-repellencywas evaluated by a test wherein liquid-repellency was measured in termsof surface tension with a wettability indicating agent.

The experiment showed that sample coat #1 is excellent in amenability tolaser abrasion, which was substantiated from the observation of theshape of the two holes one straight and the other oblique to thethickness of the coat. In addition, the sample coat #1 gave a surfacetension of about 31 dyn/cm, which is sufficiently liquid-repellent to beincorporated into a printing device.

By contrast, sample coat #3, though excellent in amenability to laserabrasion, gave a surface tension less than 31 dyn/cm, and itsliquid-repellency was found to be inadequate to be incorporated into aprinting device. Similarly, sample coat #2 sometimes developed minorflaws when subjected to abrasion with excimer laser, and thus is more orless inferior in amenability to laser abrasion. It gave a surfacetension less than 31 dyn/cm, which was found to be inadequate to beincorporated into a printing device.

From the above test results, it was demonstrated that when aliquid-repellent membrane composed of a polyimide polymer with afluorine polymer dispersed within is applied at the periphery of nozzleopening, it ensures liquid-repellency of the periphery of nozzleopening. Such arrangement further allows the nozzle to be processedeasily by abrasion with an excimer laser. It was further observed that apolyimide polymer with a fluorine polymer dispersed within presents withliquid-repellency and amenability to abrasion with excimer laser onlyafter it has turned into an imide compound.

As is obvious from the above description, the printing device of thisinvention has at least the periphery of the nozzle orifices on the sideof the printer head upon which the nozzles open their mouths coated withliquid-repellent polybenzimidazole. This ensures therebyliquid-repellency of the periphery of the nozzle orifices, and thusallow high-quality printing of documentary images.

For the production of the printing device of this invention, processingby abrasion with excimer laser can be applied because polybenzimidazoleor the material to be used for nozzles is well adapted for processing byabrasion with excimer laser. Accordingly, the printing device of thisinvention allows simplified processing of nozzles, which contributes toimproved productivity.

Still further, for the printing device of this invention, other partsthan the nozzle member of the printer head, namely, the parts excludingthe periphery of the nozzle orifices on the surface where the nozzlesopen their mouths, are made of polybenzimidazole or polyimide. Becausethese substances are highly resistant to heating, the periphery of thenozzle orifices can be made of a material that polymerizes at aconsiderably high temperature of about 150° C. or higher. Because suchmaterials are necessarily suitable for processing by abrasion withexcimer laser, the printing device of this invention will allow thenozzles of the printing head to be processed by abrasion with excimerlaser. This will help simplify necessary processes and improveproductivity. When the other parts are made of polybenzimidazole, whichis well adapted for processing by pressure molding and injectionmolding, the nozzles can be formed by a method including thoseprocedures. This will lead to a lowering of production cost and improvedproductivity.

Lastly, as detailed previously, for the printing device of thisinvention, at least the periphery of nozzle orifices and the nozzlemember on the side of the printer head upon which the nozzles open theirmouths can be made of polybenzimidazole. When such construction is used,it will be possible to employ a polybenzimidazole material having aconsiderably high polymerization temperature of about 300° C. as amaterial for the periphery of nozzle orifices.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its attendant advantages. It is therefore intendedthat such changes and modifications be covered by the appended claims.

We claim:
 1. A printing device including a printing head comprising: anejecting medium chamber; a first nozzle member including a nozzleorifice and a nozzle body, the first nozzle member in fluidcommunication with the ejecting medium chamber, the first nozzle membercomprising is made of a first polybenzimidazole; wherein a periphery ofthe nozzle orifice comprises a liquid-repellant membrane, theliquid-repellant membrane is made of a second polybenzimidazole; andwherein the first polybenzimidazole and second polybenzimidazole aredifferent.
 2. The printing device according to claim 1, wherein aperiphery of the nozzle body is made of polybenzimidazole.
 3. Theprinting device according to claim 1, wherein the nozzle member furtherincludes a pressure molded first section.
 4. The printing deviceaccording to claim 1, wherein the nozzle member further includes aninjection molded first section.
 5. The printing device according toclaim 1, wherein a second section of the nozzle member is formed byprocessing with a laser to form the nozzle orifice.
 6. The printingdevice according to claim 5, wherein the laser is an excimer laser.
 7. Aprinting device including a printer head comprising: a base plate layerhaving formed therein an ejecting medium chamber; a liquid-repellantmembrane layer formed on the base plate layer; a nozzle member formed inand extending through the base plate layer and the liquid-repellantmembrane layer, the nozzle member is in fluid communication with theejecting medium chamber; wherein the liquid-repellant membrane layer ismade of polybenzimidazole.
 8. The printing device according to claim 7wherein the base plate layer is made of polybenzimidazole.
 9. A printingdevice including a printing head, comprising: an ejecting mediumchamber; a first nozzle member including a nozzle orifice and a nozzlebody, the first nozzle member in fluid communication with the ejectingmedium chamber; wherein a periphery of the nozzle orifice is made ofpolybenzimidazole and wherein the polybenzimidazole has a waterabsorbance of 4.0% or less when the polybenzimidazole is left in an openatmosphere of 76% RH for 24 hours.
 10. A printing device including aprinting head, comprising: an ejecting medium chamber; a first nozzlemember including a nozzle orifice and a nozzle body, the first nozzlemember in fluid communication with the ejecting medium chamber; whereina periphery of the nozzle orifice is made of polybenzimidazole; andwherein the periphery of the nozzle orifice is made of apolybenzimidazole which is polymerized at 150° C. or higher.
 11. Aprinting device including a printing head, comprising: an ejectingmedium chamber; a first nozzle member including a nozzle orifice and anozzle body, the first nozzle member in fluid communication with theejecting medium chamber; wherein a periphery of the nozzle orifice ismade of polybenzimidazole; and wherein the printing head furthercomprises a metering medium chamber for housing a metering medium, asecond nozzle member in fluid communication with the metering mediumchamber, the second nozzle member being formed in the vicinity of thefirst nozzle member so as to supply the metering medium on the firstnozzle member.